First report of dragon fruit (Hylocereus undatus) stem rot caused by Diaporthe ueckerae in Taiwan

Dragon fruit (Hylocereus polyrhizus & H. undatus) is a rapidly growing commodity in Taiwan. The production acreage has been tripled since 2011, with an estimation of over 2,800 ha in 2019. From disease survey conducted in July 2020, reddish orange to blackish brown lesions similar to stem canker caused by Neoscytalidium dimidiatum on dragon fruit cladodes (Supplementary Fig. S1, Q) were observed from two orchards in Central Taiwan. Diseased cladodes were brought back to the lab, surface disinfested with 70% ethanol for 15 to 30 sec, and then blotted dried with a paper towel. Small pieces (about 3x3 mm) of necrotic spots were excised, placed on 2% water agar (WA) plates, and incubated with 12 h photoperiod at 28 ± 2 ℃ for 3 days. Among the necrotic spots that were used for fungal isolation, some were detected to have N. dimidiatum accounting for 21 isolates, while three isolates detected in other spots were unknown. Single hyphal tips of the three unknown fungal colonies with similar morphology were transferred on potato dextrose agar (PDA). Brownish- to grayish-white colonies with fluffy aerial mycelium were observed on PDA (Supplementary Fig. S1, A, B, E, F, I and J) after 8 days of incubation. To induce the sporulation, all the fungal isolates were cultivated on autoclaved cowpea pods on 2% WA plates with 12 h photoperiod at 25 ± 2 ℃ for 3 weeks. Black pycnidia embedded in cowpea tissues and creamy yellowish exudates with pycnidiospores extruding from the ostiole were observed (Supplementary Fig. S1, C, G and K). Alpha-conidia were characterized as aseptate, hyaline, smooth, ellipsoidal or fusiform, often bi-guttulate and measured about 6.0 to 6.5 μm × 2.0 to 2.3 μm (n = 50 for each isolate) (Supplementary Fig. S1, D, H and L). Beta-conidia were not observed. Morphological characteristics of these isolates were similar to Diaporthe spp. described by Udayanga et al. (2015). To further identify the fungal isolates, the internal transcribed spacer (ITS), β-tubulin (TUB) and translation elongation factor 1-α (EF1-α) regions were amplified using primer pairs ITS1/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass & Donaldson 1995) and EF1-728F/EF1-986R (Carbone & Kohn 1999), respectively. BLAST analysis of isolates CH0720-010 (ITS: OK067377; TUB: OK149767; EF1-α: OK149764), CH0720-013 (ITS: OK067378; TUB: OK149768; EF1-α: OK149765) and TC0720-016 (ITS: OK067379; TUB: OK149769; EF1-α: OK149766) showed 99.78 to 100% of ITS identity, 98.8 to 99.2% of TUB identity, and 100% of EF1-α identity with Diaporthe ueckerae (ITS: KY565426; TUB: KY569384; EF1-α: KY569388). Phylogenetic trees were constructed using concatenated ITS, TUB, and EF1-α sequences based on maximum likelihood with HKY+G model, maximum parsimony, and Bayesian inference method in MEGA X and Geneious Prime 2020.2.4. All isolates were clustered in D. ueckerae with similar topology based on aforementioned methods, hence the phylogram of maximum likelihood was presented (Supplementary Fig. S2). To confirm the pathogenicity, detached dragon fruit (H. polyrhizus and H. undatus) cladodes (20 to 30 cm in length) were surface disinfested, wounded with sterilized syringe (about 2 mm in depth), and inoculated with mycelial plugs (6 mm in diam.) from 5-day-old colonies on PDA. Each isolate had three mycelial plugs and the PDA plugs without mycelium were inoculated as negative control. Inoculated cladodes were placed in a moisture chamber and incubated at 30 ± 2 ℃ with 12 h photoperiod. Two days after inoculation (DAI), the agar plugs were removed and symptom development on the cladodes was photo recorded every other day. The inoculation experiment was repeated twice. At 6 DAI, round to irregular, dark-brown, and water-soaking lesions were observed on the cladodes of both species inoculated with the three D. ueckerae isolates whereas all negative controls remained asymptomatic (Supplementary Fig. S1, M-P). Morphologically identical fungi were re-isolated from inoculated cladodes, fulfilling Koch’s postulates. Several Diaporthe species have been reported infecting dragon fruit in the southeastern Asian countries such as Thailand, Bangladesh and Malaysia (Udayanga et al. 2012; Karim et al. 2019; Huda-Shakirah et al. 2021). To our knowledge, this is the first report of stem rot caused by D. ueckerae in Taiwan. Since the field symptoms may be easily confused with those caused by N. dimidiatum, the potential threat of Diaporthe species complex on dragon fruit should be aware and may warrant further study.

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Diaporthe species causing stem gray blight of red-fleshed dragon fruit (Hylocereus polyrhizus) in Malaysia

Scientific Reports ◽

10.1038/s41598-021-83551-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Abd Rahim Huda-Shakirah ◽

Yee Jia Kee ◽

Kak Leong Wong ◽

Latiffah Zakaria ◽

Masratul Hawa Mohd

Keyword(s):

Dna Sequences ◽

Morphological Characteristics ◽

First Report ◽

Fungal Isolates ◽

Dragon Fruit ◽

Cameron Highlands ◽

Hylocereus Undatus ◽

Hylocereus Polyrhizus ◽

Β Tubulin

AbstractThis study aimed to characterize the new fungal disease on the stem of red-fleshed dragon fruit (Hylocereus polyrhizus) in Malaysia, which is known as gray blight through morphological, molecular and pathogenicity analyses. Nine fungal isolates were isolated from nine blighted stems of H. polyrhizus. Based on morphological characteristics, DNA sequences and phylogeny (ITS, TEF1-α, and β-tubulin), the fungal isolates were identified as Diaporthe arecae, D. eugeniae, D. hongkongensis, D. phaseolorum, and D. tectonendophytica. Six isolates recovered from the Cameron Highlands, Pahang belonged to D. eugeniae (DF1 and DF3), D. hongkongensis (DF9), D. phaseolorum (DF2 and DF12), and D. tectonendophytica (DF7), whereas three isolates from Bukit Kor, Terengganu were recognized as D. arecae (DFP3), D. eugeniae (DFP4), and D. tectonendophytica (DFP2). Diaporthe eugeniae and D. tectonendophytica were found in both Pahang and Terengganu, D. phaseolorum and D. hongkongensis in Pahang, whereas D. arecae only in Terengganu. The role of the Diaporthe isolates in causing stem gray blight of H. polyrhizus was confirmed. To date, only D. phaseolorum has been previously reported on Hylocereus undatus. This is the first report on D. arecae, D. eugeniae, D. hongkongensis, D. phaseolorum, and D. tectonendophytica causing stem gray blight of H. polyrhizus worldwide.

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First Report of Flyspeck Caused by Zygophiala wisconsinensis on Sweet Persimmon Fruit in Korea

Plant Disease ◽

10.1094/pdis-12-10-0917 ◽

2011 ◽

Vol 95 (5) ◽

pp. 616-616 ◽

Cited By ~ 1

Author(s):

J. Kim ◽

O. Choi ◽

J.-H. Kwon

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Its Rdna ◽

Control Treatment ◽

Diospyros Kaki ◽

Distilled Water ◽

First Report ◽

Persimmon Fruit ◽

Fungal Isolates ◽

Agar Disc

Sweet persimmon (Diospyros kaki L.), a fruit tree in the Ebenaceae, is cultivated widely in Korea and Japan, the leading producers worldwide (2). Sweet persimmon fruit with flyspeck symptoms were collected from orchards in the Jinju area of Korea in November 2010. The fruit had fungal clusters of black, round to ovoid, sclerotium-like fungal bodies with no visible evidence of a mycelial mat. Orchard inspections revealed that disease incidence ranged from 10 to 20% in the surveyed area (approximately 10 ha) in 2010. Flyspeck symptoms were observed on immature and mature fruit. Sweet persimmon fruit peels with flyspeck symptoms were removed, dried, and individual speck lesions transferred to potato dextrose agar (PDA) and cultured at 22°C in the dark. Fungal isolates were obtained from flyspeck colonies on 10 sweet persimmon fruit harvested from each of three orchards. Fungal isolates that grew from the lesions were identified based on a previous description (1). To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) rDNA sequence of a representative isolate was amplified and sequenced using primers ITS1 and ITS4 (4). The resulting 552-bp sequence was deposited in GenBank (Accession No. HQ698923). Comparison with ITS rDNA sequences showed 100% similarity with a sequence of Zygophiala wisconsinensis Batzer & Crous (GenBank Accession No. AY598855), which infects apple. To fulfill Koch's postulates, mature, intact sweet persimmon fruit were surface sterilized with 70% ethanol and dried. Three fungal isolates from this study were grown on PDA for 1 month. A colonized agar disc (5 mm in diameter) of each isolate was cut from the advancing margin of a colony with a sterilized cork borer, transferred to a 1.5-ml Eppendorf tube, and ground into a suspension of mycelial fragments and conidia in a blender with 1 ml of sterile, distilled water. The inoculum of each isolate was applied by swabbing a sweet persimmon fruit with the suspension. Three sweet persimmon fruit were inoculated per isolate. Three fruit were inoculated similarly with sterile, distilled water as the control treatment. After 1 month of incubation in a moist chamber at 22°C, the same fungal fruiting symptoms were reproduced as observed in the orchards, and the fungus was reisolated from these symptoms, but not from the control fruit, which were asymptomatic. On the basis of morphological characteristics of the fungal colonies, ITS sequence, and pathogenicity to persimmon fruit, the fungus was identified as Z. wisconsinensis (1). Flyspeck is readily isolated from sweet persimmon fruit in Korea and other sweet persimmon growing regions (3). The exposure of fruit to unusual weather conditions in Korea in recent years, including drought, and low-temperature and low-light situations in late spring, which are favorable for flyspeck, might be associated with an increase in occurrence of flyspeck on sweet persimmon fruit in Korea. To our knowledge, this is the first report of Z. wisconsinensis causing flyspeck on sweet persimmon in Korea. References: (1) J. C. Batzer et al. Mycologia 100:246, 2008. (2) FAOSTAT Database. Retrieved from http://faostat.fao.org/ , 2008. (3) H. Nasu and H. Kunoh. Plant Dis. 71:361, 1987. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, Inc., New York, 1990.

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First report of Coniella castaneicola causing leaf blight on blueberry (Vaccinium virgatum) in China

Plant Disease ◽

10.1094/pdis-05-21-1122-pdn ◽

2021 ◽

Author(s):

Jiahao Lai ◽

Guihong Xiong ◽

Bing Liu ◽

Weigang Kuang ◽

Shuilin Song

Keyword(s):

Molecular Identification ◽

Morphological Characteristics ◽

Leaf Blight ◽

Yield Potential ◽

Effective Control ◽

Economic Losses ◽

Distilled Water ◽

First Report ◽

Fungal Isolates ◽

Blight Disease

Blueberry (Vaccinium virgatum), an economically important small fruit crop, is characterized by its highly nutritive compounds and high content and wide diversity of bioactive compounds (Miller et al. 2019). In September 2020, an unknown leaf blight disease was observed on Rabbiteye blueberry at the Agricultural Science and Technology Park of Jiangxi Agricultural University in Nanchang, China (28°45'51"N, 115°50'52"E). Disease surveys were conducted at that time, the results showed that disease incidence was 90% from a sampled population of 100 plants in the field, and this disease had not been found at other cultivation fields in Nanchang. Leaf blight disease on blueberry caused the leaves to shrivel and curl, or even fall off, which hindered floral bud development and subsequent yield potential. Symptoms of the disease initially appeared as irregular brown spots (1 to 7 mm in diameter) on the leaves, subsequently coalescing to form large irregular taupe lesions (4 to 15 mm in diameter) which became curly. As the disease progressed, irregular grey-brown and blighted lesion ran throughout the leaf lamina from leaf tip to entire leaf sheath and finally caused dieback and even shoot blight. To identify the causal agent, 15 small pieces (5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface-sterilized in 75% ethanol solution for 30 sec and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water, and then incubated on potato dextrose agar (PDA) at 28°C for 5-7 days in darkness. Five fungal isolates showing similar morphological characteristics were obtained as pure cultures by single-spore isolation. All fungal colonies on PDA were white with sparse creeping hyphae. Pycnidia were spherical, light brown, and produced numerous conidia. Conidia were 10.60 to 20.12 × 1.98 to 3.11 µm (average 15.27 × 2.52 µm, n = 100), fusiform, sickle-shaped, light brown, without septa. Based on morphological characteristics, the fungal isolates were suspected to be Coniella castaneicola (Cui 2015). To further confirm the identity of this putative pathogen, two representative isolates LGZ2 and LGZ3 were selected for molecular identification. The internal transcribed spacer region (ITS) and large subunit (LSU) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004) and LROR/LR7 (Castlebury and Rossman 2002). The sequences of ITS region (GenBank accession nos. MW672530 and MW856809) showed 100% identity with accessions numbers KF564280 (576/576 bp), MW208111 (544/544 bp), MW208112 (544/544 bp) of C. castaneicola. LSU gene sequences (GenBank accession nos. MW856810 to 11) was 99.85% (1324/1326 bp, 1329/1331 bp) identical to the sequences of C. castaneicola (KY473971, KR232683 to 84). Pathogenicity was tested on three blueberry varieties (‘Rabbiteye’, ‘Double Peak’ and ‘Pink Lemonade’), and four healthy young leaves of a potted blueberry of each variety with and without injury were inoculated with 20 μl suspension of prepared spores (106 conidia/mL) derived from 7-day-old cultures of LGZ2, respectively. In addition, four leaves of each variety with and without injury were sprayed with sterile distilled water as a control, respectively. The experiment was repeated three times, and all plants were incubated in a growth chamber (a 12h light and 12h dark period, 25°C, RH greater than 80%). After 4 days, all the inoculated leaves started showing disease symptoms (large irregular grey-brown lesions) as those observed in the field and there was no difference in severity recorded between the blueberry varieties, whereas the control leaves showed no symptoms. The fungus was reisolated from the inoculated leaves and confirmed as C. castaneicola by morphological and molecular identification, fulfilling Koch’s postulates. To our knowledge, this is the first report of C. castaneicola causing leaf blight on blueberries in China. The discovery of this new disease and the identification of the pathogen will provide useful information for developing effective control strategies, reducing economic losses in blueberry production, and promoting the development of the blueberry industry.

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First Report of Occurrence of Eggplant Wilt Caused by Verticillium dahliae in Korea

Plant Disease ◽

10.1094/pdis.2000.84.10.1152a ◽

2000 ◽

Vol 84 (10) ◽

pp. 1152-1152

Author(s):

S. K. Kim ◽

S. S. Hong ◽

K. W. Kim ◽

E. W. Park

Keyword(s):

Verticillium Dahliae ◽

Solanum Melongena ◽

Morphological Characteristics ◽

Wilt Disease ◽

Potato Dextrose Agar ◽

First Report ◽

Vascular Tissues ◽

Fungal Isolates ◽

Pathogenicity Tests ◽

Root Cutting

A wilt disease occurred on greenhouse-grown eggplants (Solanum melongena L.) at Hanam and Yeojoo, Korea, in 1997. Lower leaves on the 2-month-old wilted eggplants exhibited gradual yellowing, interveinal necrosis, and marginal crinkling and dropped prematurely. Vascular tissues of diseased stems were discolored and turned black. Vertical sections of the stems revealed that the pith had been colonized by the fungus. The disease progressed from lower parts of the plants upward. Incidence of diseased eggplants in greenhouses was 5% on 23 May 1997. Although the incidence increased to 10% on 13 June, it remained constant through early July. Fungal isolates from discolored vascular tissues were initially whitish to cream color on potato-dextrose agar, which turned black due to the formation of microsclerotia. The fungus also produced abundant verticillate conidiophores with phialides and conidia. Based on these cultural and morphological characteristics, the fungus was identified as Verticillium dahliae Klebahn. Pathogenicity tests by root cutting, root dipping, or soil drenching resulted in similar symptoms observed in the naturally infected eggplants. Symptoms were first observed on lower leaves of each eggplant 3 weeks after inoculation. Isolation from symptomatic leaves of the inoculated eggplants yielded V. dahliae. This is the first report of occurrence of Verticillium wilt of eggplant in Korea.

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First report of Leptosphaeria biglobosa ‘canadensis’ causing blackleg on oilseed rape (Brassica napus) in China

Plant Disease ◽

10.1094/pdis-12-20-2735-pdn ◽

2021 ◽

Author(s):

Tao Luo ◽

Guoqing Li ◽

Long Yang

Keyword(s):

Brassica Napus ◽

Oilseed Rape ◽

Southern China ◽

Disease Incidence ◽

Morphological Characteristics ◽

Gansu Province ◽

Bootstrap Support ◽

First Report ◽

Fungal Isolates ◽

Leptosphaeria Biglobosa

Oilseed rape (Brassica napus L.) is one of the most important oilseed crops in China. It is widely cultivated in China, with winter oilseed rape in Yangtze River basin and in southern China, and spring oilseed rape in northern China. In August 2017, a survey for Leptosphaeria spp. on spring oilseed rape was conducted in Minle county, Zhangye city, Gansu Province, China. The symptoms typical of blackleg on basal stems of oilseed rape were observed in the field. A large number of black fruiting bodies (pycnidia) were present on the lesions (Fig. 1A). The disease incidence of basal stem infection in the surveyed field was 19%. A total of 19 diseased stems were collected to isolate the pathogen. After surface sterilizing (75% ethanol for 30 s, 5% NaOCl for 60 s, followed by rinsing in sterilized water three times), diseased tissues were cultured on acidified potato dextrose agar (PDA) plates at 20°C for 7 days. Twelve fungal isolates were obtained. All fungal isolates produced typical tan pigment on PDA medium, and produced pycnidia after two weeks (Fig. 1B). Colony morphological characteristics indicated that these isolates might belong to Leptosphaeria biglobosa. To confirm identification, multiple PCR was conducted using the species-specific primers LmacF, LbigF, LmacR (Liu et al. 2006). Genomic DNA of each isolate was extracted using the cetyltrimethylammonium bromide (CTAB) method. DNA samples of L. maculans isolate UK-1 and L. biglobosa isolate W10 (Cai et al. 2015) were used as references. Only a 444-bp DNA band was detected in all 12 isolates and W10, whereas a 333-bp DNA band was detected only in the UK-1 isolate (Fig. 1C). PCR results suggested that these 12 isolates all belong to L. biglobosa. In addition, the internal transcribed spacer (ITS) region of these 12 isolates was analyzed for subspecies identification (Vincenot et al. 2008). Phylogenetic analysis based on ITS sequence showed that five isolates (Lb1134, Lb1136, Lb1138, Lb1139 and Lb1143) belonged to L. biglobosa ‘brassicae’ (Lbb) with 78% bootstrap support, and the other seven isolates (Lb1135, Lb1137, Lb1140, Lb1141, Lb1142, Lb1144 and Lb1145) belonged to L. biglobosa ‘canadensis’ (Lbc) with 95% bootstrap support (Fig. 1D). Two Lbb isolates (Lb1134 and Lb1136) and two Lbc isolates (Lb1142 and Lb1144) were randomly selected for pathogenicity testing on B. napus cultivar Zhongshuang No. 9 (Wang et al. 2002). Conidial suspensions (10 μL, 1 × 107 conidia mL-1) of these four isolates were inoculated on needle-wounded cotyledons (14-day-old seedling), with 10 cotyledons (20 wounded sites) per isolate. A further 10 wounded cotyledons were inoculated with water and served as controls. Seedlings were maintained in a growth chamber at 20°C with 100% relative humidity and a 12-h photoperiod. After 7 days, cotyledons inoculated with the four isolates showed necrotic lesions in the inoculated wounds. Control cotyledons had no symptoms (Fig. 2). Fungi re-isolated from the infected cotyledons showed similar colony morphology as the original isolates. Therefore, L. biglobosa ‘brassicae’ and L. biglobosa ‘canadensis’ appear to be the pathogens causing the observed blackleg symptoms on spring oilseed rape in Gansu, China. In previous studies, L. biglobosa ‘brassicae’ has been found in many crops in China, including oilseed rape (Liu et al. 2014; Cai et al. 2015), Chinese radish (Raphanus sativus) (Cai et al. 2014a), B. campestris ssp. chinensis var. purpurea (Cai et al. 2014b), broccoli (B. oleracea var. italica) (Luo et al. 2018), ornamental kale (B. oleracea var. acephala) (Zhou et al. 2019a), B. juncea var. multiceps (Zhou et al. 2019b), B. juncea var. tumida (Deng et al. 2020) and Chinese cabbage (B. rapa subsp. pekinensis) (Yu et al. 2021 accepted). To the best of our knowledge, this is the first report of L. biglobosa ‘canadensis’ causing blackleg on B. napus in China.

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First Report of Sclerotinia Blight on Peanut Caused by Sclerotinia sclerotiorum in Qinghai Province, China

Plant Disease ◽

10.1094/pdis-07-21-1503-pdn ◽

2021 ◽

Author(s):

Xia Zhang ◽

Wenrong Xian ◽

Mingjing Qu ◽

Manlin Xu ◽

zhiqing Guo ◽

...

Keyword(s):

Sclerotinia Sclerotiorum ◽

Early Stage ◽

Morphological Characteristics ◽

Broad Host Range ◽

Heat Shock Protein 60 ◽

Potential Threat ◽

Qinghai Province ◽

First Report ◽

Sequence Identity ◽

Sclerotinia Blight

Historically, peanut has not been produced in Qinghai province located in Northwest China because of the high elevation and cold climates. However, since 2020 field studies have been conducted to evaluate peanut cultivars for suitability to field production. In 2020, peanut cultivation was successful for the first time in Haidong city, Qinghai province, China. In August 2020, brown, irregular-shaped lesions were observed on peanut stems from Qinghai province in China. In the early stage, the watersoaked spots were formed on the stems, then lesions expanded rapidly and became brown. In advanced stages of the disease, stems became bleached and eventually died. The inside of the stems was rotten and hollow, and the diseased stem wilted and died. White hyphae and black irregular shaped sclerotia were observed on the infected stems. Finally, local or whole plant rotted and died at the end. Approximately 10% of the plants in a field were infected. Symptomatic stems were cut into small pieces, disinfected with 75% ethanol for 1 minute, 0.5% NaClO for two minutes, and sterile water for three times. Pieces then were plated on potato dextrose agar (PDA) media and incubated at 25°C in darkness. Fungal colonies were initially white, becoming gray, then black sclerotia (2.4 to 6.0 mm in diameter) were appeared at the edge of colonies. Genomic DNA of the pure cultures of an isolate (ZHX7) was extracted and PCR was carried out using glyceraldehydes-3-phosphate dehydrogenase gene (G3PDH) region primers G3PDH-F/G3PDH-R, heat-shock protein 60 gene (HSP60) region primers HSP60-F/HSP60-R, and DNA-dependent RNA polymerase subunit gene (RPB2) region primers RPB2-F/RPB2-R (Staats et al., 2005), respectively. G3PDH region (Accession No. MZ388475) showed 99.44% sequence identity (887 bp out of 909 bp) to Sclerotinia sclerotiorum (Accession No. AJ705044, 887 bp out of 887 bp). HSP60 region (Accession No. MZ388476) showed 99.90% sequence identity (972 bp out of 984bp) to S. sclerotiorum (Accession No. AJ716048, 972 bp out of 980 bp). RPB2 region (Accession No. MZ388477) showed 100.00% sequence identity (1096 bp out of 1129 bp) to S. sclerotiorum (Accession No. AJ745716, 1096 bp out of 1096 bp). Phylogenetic analysis was done using Neighbor-Joining (NJ) analysis based on those gene sequences. The isolate was identified as S. sclerotiorum based on molecular analysis and morphological characteristics. For pathogenicity assay, ten-days-old potted peanut (Luhua No.12) seedlings were inoculated with one mycelial plug (8 mm in diameter ) by placing the inoculum on the base of the stem in a growth chamber (30°C in the day and 25°C at night, a 12-h photoperiod and 80% RH). All inoculated seedlings exhibited typical basal stem rot, and root showed different degrees of damage, and wilted 5 days after inoculation. No symptoms were observed on control plants treated with sterile distilled mycelial plugs, and S. sclerotiorum was consistently re-isolated from symptomatic tissue. S. sclerotiorum has been reported on peanut in Northeastern China (Yan et al., 2005). To our knowledge, this is the first report of S. sclerotiorum causing Sclerotinia Blight on peanut in Qinghai province, China. The peanut planting area in Qinghai has been further expanded this year, and S. sclerotiorum has a broad host range (Boland and Hall, 1994), so Sclerotinia Blight is a potential threat to peanut production, and as a result, it is critical for commercial producers to monitor plants for S. sclerotiorum.

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First report of Curvularia plantarum causing leaf spot on sweet potato (Ipomoea batatas) in China

Plant Disease ◽

10.1094/pdis-08-21-1665-pdn ◽

2021 ◽

Author(s):

Jiahao Lai ◽

Tongke Liu ◽

Bing Liu ◽

Weigang Kuang ◽

Shuilin Song

Keyword(s):

Sweet Potato ◽

Molecular Identification ◽

Leaf Spot ◽

Ipomoea Batatas ◽

Morphological Characteristics ◽

Distilled Water ◽

Gene Sequences ◽

First Report ◽

Potted Plants ◽

Fungal Isolates

Sweet potato [Ipomoea batatas (L.) Lam], is an extremely versatile vegetable that possesses high nutritional values. It is also a valuable medicinal plant having anti-cancer, antidiabetic, and anti-inflammatory activities. In July 2020, leaf spot was observed on leaves of sweet potato in Nanchang, China (28°45'51"N, 115°50'52"E), which affected the growth and development of the crop and caused tuberous roots yield losses of 25%. The disease incidence (total number of diseased plants / total number of surveyed plants × 100%) was 57% from a sampled population of 100 plants in the field. Symptomatic plants initially exhibited small, light brown, irregular-shaped spots on the leaves, subsequently coalescing to form large irregular brown lesions and some lesions finally fell off. Fifteen small pieces (each 5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface sterilized in 75% ethanol solution for 30 sec and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water and incubated on potato dextrose agar (PDA) plates at 28°C in darkness. A total of seven fungal isolates with similar morphological characteristics were obtained as pure cultures by single-spore isolation. After 5 days of cultivation at 28°C, dark brown or blackish green colonies were observed, which developed brown, thick-walled, simple, or branched, and septate conidiophores. Conidia were 18.28 to 24.91 × 7.46 to 11.69 µm (average 21.27 × 9.48 µm, n = 100) in size, straight or slightly curved, middle cell unequally enlarged, brown to dark brown, apical, and basal cells slightly paler than the middle cells, with three septa. Based on morphological characteristics, the fungal isolates were suspected to be Curvularia plantarum (Raza et al. 2019). To further confirm the identification, three isolates (LGZ1, LGZ4 and LGZ5) were selected for molecular identification. The internal transcribed spacer region (ITS), glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), and translation elongation factor 1-alpha (EF1-α) genes were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004), gpd1/gpd2 (Berbee et al. 1999), EF-983F/EF-2218R (Rehner and Buckley 2005), respectively. The sequences of ITS region of the three isolates (accession nos. MW581905, MZ209268, and MZ227555) shared 100% identity with those of C. plantarum (accession nos. MT410571-72, MN044754-55). Their GAPDH gene sequences were identical (accession nos. MZ224017-19) and shared 100% identity with C. plantarum (accession nos. MN264120, MT432926, and MN053037-38). Similarly, EF1-α gene sequences were identical (accession nos. MZ224020-22) and had 100% identity with C. plantarum (accession nos. MT628901, MN263982-83). A maximum likelihood phylogenetic tree was built based on concatenated data from the sequences of ITS, GAPDH, and EF-1α by using MEGA 5. The three isolates LGZ1, LGZ4, and LGZ5 clustered with C. plantarum. The fungus was identified as C. plantarum by combining morphological and molecular characteristics. Pathogenicity tests were conducted by inoculating a conidial suspension (106 conidia/ml) on three healthy potted I. batatas plants (five leaves wounded with sterile needle of each potted plant were inoculated). In addition, fifteen wounded leaves of three potted plants were sprayed with sterile distilled water as a control. All plants were maintained in a climate box (12 h light/dark) at 25°C with 80% relative humidity. All the inoculated leaves started showing light brown flecks after 7 days, whereas the control leaves showed no symptoms. The pathogenicity test was conducted three times. The fungus was reisolated from all infected leaves of potted plants and confirmed as C. plantarum by morphological and molecular identification, fulfilling Koch’s postulates. To our knowledge, this is the first report of C. plantarum causing leaf spot on sweet potato in China. The discovery of this new disease and the identification of the pathogen will contribute to the disease management, provide useful information for reducing economic losses caused by C. plantarum, and lay a foundation for the further research of resistance breeding.

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Characterization of Alternaria isolates causing leaf spots in radish in Brazil

Summa Phytopathologica ◽

10.1590/0100-5405/233817 ◽

2020 ◽

Vol 46 (4) ◽

pp. 340-341

Author(s):

Cléia Santos Cabral ◽

Elenice Alves Barboza ◽

Luiz Henrique Rocha Lopes ◽

Maurício Rossato ◽

Rafaela Cristina Ferreira Borges ◽

...

Keyword(s):

Phylogenetic Analysis ◽

Morphological Characteristics ◽

Phytopathogenic Fungus ◽

Morphological Markers ◽

Phylogenetic Species ◽

Koch’S Postulates ◽

First Report ◽

Leaf Spots ◽

Necrotic Spots

ABSTRACT Alternaria japonica Yoshii, an important cruciferous phytopathogenic fungus, has been identified in radish plants showing symptoms of necrotic spots with chlorotic halos. The samples were collected from the cities of Brasília-DF and Guaraciaba do Norte-CE, Brazil. The isolates are deposited in the collection of fungi and oomycetes of “Embrapa Hortaliças”. Using the concept of morphological and phylogenetic species, two isolates were selected (EH-945 and EH-1379) for identification. Through the evaluation of morphological markers, the isolates were concluded to be similar to A. japonica. Based on the phylogenetic analysis, the isolates grouped with A. japonica reference isolates ATCC 13618 and CBS 118390. To complete Koch’s postulates, radish, arugula, mustard and turnip plants were inoculated. All species showed symptoms similar to those originally reported in the field (except for non-inoculated controls) seven to 12 days after inoculation. The isolates obtained from symptomatic plants showed morphological characteristics identical to those of the pathogen. This is the first report of radish as a host of A. japonica in Brazil.

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First Report of Postharvest Blue Mold decay caused by Penicillium expansum on Lemon (Citrus limon) fruit in China

Plant Disease ◽

10.1094/pdis-10-20-2239-pdn ◽

2021 ◽

Author(s):

Ibatsam Khokhar ◽

Jianming Chen ◽

Junhuan Wang ◽

Yang Jia ◽

Yanchun Yan ◽

...

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

Penicillium Expansum ◽

Citrus Limon ◽

Conidial Suspension ◽

Blue Mold ◽

Causal Organism ◽

Lemon Fruit ◽

First Report ◽

Fungal Isolates

Lemon (Citrus limon) is one of the most important commercial (both dried and fresh) citrus fruits in China. In the spring of 2019, postharvest blue mold decay was observed at an incidence of 3-5% on lemon fruit at the local markets in Beijing, China. Fruit lesions were circular, brown, soft, and watery, and rapidly expanded at 25°C. To isolate the causal organism, small pieces (2 mm3) were cut from the lesions, surface-sterilized for 1 min in 1.5% NaOCl, rinsed three times with sterilized water, dried with sterile filter paper, placed onto potato dextrose agar (PDA) medium, and incubated at 25°C for 6 days. Eight morphologically similar single-colony fungal isolates were recovered from six lemon fruit. Colony surfaces were bluish-green on the upper surface and cream to yellow-brown one the reverse. Hyphae on colony margins were entirely subsurface and cream in color. Mycelium was highly branched, septate, and colorless, and conidiophores were 250 to 450 × 3.0 to 4.0 µm in size. Stipe of conidiophores were smooth-walled, bearing terminal penicilli, typically terverticillate or less commonly birverticillate, rami occurring singly, 16 to 23 × 3.0 to 4.0 µm, metulae in 3 to 6, measuring 12 to 15 × 3.0 to 4.0 µm. Phialides were ampulliform to almost cylindrical, in verticils of 5 to 8, measuring 8 to 11 × 2.5 to 3.2 µm with collula. Conidia were smooth-walled, ellipsoidal, measuring 3.0 to 3.5 × 2.5 to 3.0 µm. According to morphological characteristics, the fungus was identified as Penicillium expansum (Visagie et al. 2014). For molecular identification, genomic DNA of eight fungal isolates was extracted, regions of the beta-tubulin (TUB), and calmodulin (CAL) genes and ITS region, were amplified using Bt2a/Bt2b, CAL-228F/ CAL-737, and ITS1/ITS4 primers respectively. Obtained sequences of all isolates were identical to sequences of the representative isolate YC-IK12, which was submitted in the GenBank. BLAST results of YC-IK12 sequences (ITS; MT856700: TUB; MT856958: CAL; MT856959) showed 98 to 100% similarity with P. expansum accessions (NR-077154, LN896428, JX141581). For pathogenicity tests, 10 μl of conidial suspension (10 × 105 conidia/ml) from seven-day-old YC-IK12 culture was inoculated using a sterilized needle into the surface of each five asymptomatic disinfected lemons. As a control, three lemons were inoculated using sterile distilled water. All inoculated lemons were placed in plastic containers and incubated at 25°C for 7 days. Decay lesions, identical to the original observations, developed on all inoculated lemons, while control lemons remained asymptomatic. Fungus re-isolated from the inoculated lemon was identified as P. expansum on the basis morphology and Bt2a/Bt2b, CAL-228F/ CAL-737, and ITS1/ITS4 sequences. Previously, Penicillium spp. including P. expansum have been reported as post-harvest pathogens on various Citrus spp. (Louw & Korsten 2015). However, P. digitatum has been reported on lemons and P. expansum has been reported on stored Kiwifruit (Actinidia arguta), Malus, and Pyrus species in China (Tai, 1979; Wang et al. 2015). To our knowledge, this is the first report of blue mold caused by P. expansum on lemons in China. References Louw, J. P., Korsten, L. 2015. Plant Dis. 99:21-30. Tai, F.L. 1979. Sylloge Fungorum Sinicorum. Sci. Press, Acad. Sin., Peking, 1527 pages. 8097 Visagie, C.M. et al. 2014. Studies. Mycol.78: 343. Wang, C. W. et al. 2015. Plant Dis. 99:1037.

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First Report of Dieback of Camellia azalea Caused by Glomerella cingulata f. sp. camelliae in Guangdong, China

Plant Disease ◽

10.1094/pdis-04-14-0425-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1583-1583 ◽

Cited By ~ 1

Author(s):

S. Sun ◽

J. Wang ◽

H. Zhao ◽

M. Zhang ◽

C. Shu ◽

...

Keyword(s):

Average Rate ◽

Morphological Characteristics ◽

Guangdong Province ◽

Middle Part ◽

Individual Plant ◽

Conidial Suspension ◽

Glomerella Cingulata ◽

Single Spore ◽

First Report ◽

Necrotic Spots

Camellia azalea Wei (Theaceae) is a critically endangered species with high ornamental value in China. Its wild individual plants, less than 1,000, are only found in Yangchun, Guangdong Province, China. Since 2010, a severe dieback on C. azalea has been observed in several commercial plantations in Foshan, Guangdong Province, during the process of artificial propagation. The infection started from the middle portion of the new shoots, where necrosis spots developed and expanded to girdle the stems. Consequently, the shoots died and became brown in color. Later, the necrotic spots turned pale gray, and many small, black fruiting bodies emerged. In the end, more than half of the dead shoots broke off from the necrotic spots. Generally, about 10 to 20% new shoots were infected for one individual plant. Although the older branches with leaves were not infected and showed no symptoms, the dieback of crown outer layer greatly reduced the ornamental value of the plants and the sale price went down. Another part of the plants that is often infected is the stalk, resulting in the drop of fruits. By using routine isolation methods and single-spore purification technique, 18 single-conidial isolates with similar colony morphology were obtained from five diseased plants. The cultures of single-conidial isolates grew at an average rate of 6.8 mm per day on PDA at 28°C. The central part of colony became gray-green with age, and acervuli formed on the medium after incubation for 7 to 10 days. Conidia, round at both ends, were 13.65 to 18.3 × 3.61 to 5.92 μm (avg. = 16.1 ± 1.6 × 4.8 ± 0.8 μm, n = 50) in size. After culturing for 50 to 60 days, perithecia matured. Ascopores were hyaline, straight, aseptate, and 10.02 to 13.77 × 3.27 to 4.45 μm (avg. = 12.2 ± 1.1 × 3.9 ± 0.4 μm, n = 50) in size. The cultural and morphological characteristics of these isolates are consistent with the description of Glomerella cingulata f. sp. camelliae (1). The sequences (GenBank Accession Nos. KJ668576, KJ668577, KJ676642, KJ689374, KJ689375, and KJ689376) of ITS, GPDH, GS, actin, β-tubulin, and CAL regions of three representative isolates are identical and share 99, 99, 100, 99, 100, and 100% identity with those of the type specimen of G. cingulata f. sp. camelliae ICMP 10643 (JX010224, JX009908, JX010119, JX009540, JX010436, and JX009630), respectively (2). Twenty randomly selected shoots with young leaves on the top of them, detached from different trees, were scratched in the middle part with a fine scalpel to generate a 5-mm-long wound, 50 μl conidial suspension (1 × 105 conidia ml−1) was then dropped onto the wound for inoculation. The control shoots were inoculated with the same volume of sterile distilled water. All inoculated shoots were placed into an intelligent artificial climate incubator with 12-h photoperiod and 100% relative humidity at 28 ± 1°C. Each treatment replicated on five shoots, and the tests were repeated twice. Symptoms resembling those in the field were observed on all conidia-inoculated shoots after 10 to 14 days, and control shoots were asymptomatic. The same fungus G. cingulata f. sp. camelliae was consistently re-isolated from the diseased shoots, fulfilling Koch's postulates. G. cingulata f. sp. camelliae has been reported on other species of Camellia outside China, but this is the first report in China where the species is endemic and endangered (1,2). References: (1) J. S. W. Dickens et al. Plant Pathol. 38:75, 1989. (2) B. Weir et al. Stud Mycol. 73:115, 2012.

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